Water treatment systems are commonly used in water supply systems. In a residential water supply system, for example, water softeners, acid neutralizers, iron/manganese removal systems, arsenic removal systems, and aeration systems may be used to filter or treat the water being supplied from a water source (e.g., from a well or city water supply). To facilitate the removal of contaminants, such as iron, manganese, and sulfur, some water treatment systems aerate the water to provide oxidation prior to the filtering. In such systems, a head of air may be maintained at the top of a water treatment tank such that the water provided to the tank passes through the head of air before passing through filter media.
Some existing water treatment systems include a control valve (e.g., connected to the top of the tank) to control the water passing in to and out of the system according to water treatment operating cycles. To provide the head of air in an existing water treatment system that uses aeration, the control valve may perform an air draw cycle by directing water through a venturi coupled to an air inlet such that the venturi draws air into the top of the filter tank with the water directed to the top of the tank while also directing water from the bottom of the tank to a drain. During a service cycle, the control valve directs the water to flow through the trapped air in the tank, through filter media in the tank, and then to a service water system (e.g., a residential water system). To provide air regeneration in these existing water treatment systems, a control valve first initiates a backwash cycle that opens a drain line to release or discharge the old compressed air in the tank while directing water to the bottom of the filter tank to backwash the filter media.
The use of these existing water treatment systems with a venturi providing aeration presents several drawbacks. One such drawback is the noise and rattling of the drain line when the compressed air charge is released suddenly during the backwash cycle. If the drain line is not properly secured, this may also cause unwanted splashing, breaks and/or flooding. The rapid air escape may also cause the filter media to jump vertically inside the filter tank, causing it to be lost through the drain line and possibly causing plugging of the drain and flooding. To avoid this, existing systems often use less filter media and approximately 25% of the filter bed depth may be lost, requiring more frequent air regenerations, wasted water and wasted electricity. Using a larger tank results in more water going to drain during an air draw cycle and an increased cost of the filter media.
Another drawback of the existing water treatment systems using a venturi to provide aeration is the wasted water that must pass through the venturi to introduce sufficient air into the filter tank. In a residential system that regenerates every night and takes 1 gallon of water to introduce 1.75 gallons of air, for example, over 2,500 gallons of water per year may be lost or the equivalent of 100 ten minute showers per year. The use of untreated water through the venturi to provide the aeration may also cause the venturi to become clogged with iron and stop drawing air, which may cause the filter to bleed contaminants into the residential water supply.
A further drawback of the existing systems using a venturi to provide aeration is the need for a complete air regeneration cycle (e.g., a backwash cycle before an air draw cycle) to provide a new charge of air. Thus, these existing systems may not be recharged with air while remaining in service.